1. Field of the Invention
This invention relates generally to perpendicular magnetic recording write heads, and more particularly to a method for making the write pole of a write head for use in a magnetic recording hard disk drive.
2. Description of the Related Art
Perpendicular magnetic recording, wherein the recorded bits are stored in a perpendicular or out-of-plane orientation in the recording layer, is a promising path toward ultra-high recording densities in magnetic recording hard disk drives. As shown in FIG. 1A, a “dual-layer” medium includes a perpendicular magnetic data recording layer (RL) on a “soft” or relatively low-coercivity magnetically permeable underlayer (SUL) formed on the disk substrate. This type of medium is shown with a single write pole (WP) type of recording head. A thin film coil (C) is shown in section between the WP and the return pole (RP) of the recording head. Write current through coil C induces a magnetic field (shown by dashed line 10) from the WP that passes through the RL (to magnetize the region of the RL beneath the WP), through the flux return path provided by the SUL, and back to the RP. The recording head is typically formed on an air-bearing slider that has its air-bearing surface (ABS) supported above the RL of the medium. In FIG. 1A, the medium moves past the recording head in the direction indicated by arrow 20. The RL is illustrated with perpendicularly recorded or magnetized regions, with adjacent regions having opposite magnetization directions, as represented by the arrows. The magnetic transitions between adjacent oppositely-directed magnetized regions are detectable by the read head (not shown) as the recorded bits.
FIG. 1A also shows a section of a trailing shield (TS) with a trailing shield notch (TSN) that is near the WP but spaced from the WP by a gap of nonmagnetic material. The use of a TS separated from the WP by a nonmagnetic gap slightly alters the angle of the write field and makes writing more efficient. The TSN causes a stronger magnetic field below the WP and sharper magnetic transitions written by the head, which is desirable. FIG. 1B is a view in the direction 1B-1B of FIG. 1A and illustrates the width of the WP to substantially define the trackwidth (TW) of the data recorded in the RL. The TS is substantially wider than the WP in the cross-track direction but the TSN portion is generally the same width as the WP. FIG. 2 is a perspective view showing the relationship between the WP, the TS with TSN, and the recording medium with the RL and SUL. FIG. 3 is a view of the slider ABS, as seen from the disk, and shows portions of the write head, with details of the WP, the TSN and the gap between the WP and the TSN. The WP has an end 40 generally parallel to the ABS and a trailing edge 42 that is generally orthogonal to the along-the-track direction and generally defines the TW.
FIG. 3 shows a WP, gap layer and TS for a just single write head. However a large number of write heads are fabricated simultaneously from a single wafer using semiconductor fabrication processes. The gap typically includes an oxide mask layer (such as Al2O3 or SiO2) as a result of the conventional fabrication process wherein the oxide mask layer is formed over the layer of magnetic material used to form the WP. A resist is formed over the oxide mask and the structure is then ion milled to form the WP. After removal of the resist, the oxide mask remains above the WP. A thin film 50 of additional electrically conductive gap material, such as Ta or Rh, may optionally be deposited over the oxide mask, followed by electroplating of the magnetic material, typically NiFe, to form the TSN and the remainder of the TS.
The method for patterning the WP to the desired shape and TW requires the use of a silicon-containing hard mask layer, such as silicon dioxide (SiO2), which is used to pattern the resist layer in the desired shape for subsequent patterning of the WP. The hard mask requires the use of an adhesion layer on the resist layer and reactive ion etching (RIE) in a fluorine-containing gas. The RIE process is difficult to control, making it difficult to uniformly pattern a large number of write heads on a single wafer. Additionally, the use of RIE requires the interruption of the fabrication process because the wafer must be removed from the RIE tool for the subsequent ion milling to form the WP.
What is needed is a method for making the write pole of a perpendicular magnetic recording write head that does not require RIE or multiple processing stations and that results in a write pole with a more precisely defined TW.